Enemy's wont die if spawned

I have some simple scripts which destroys my enemy when my bullet collides with them, this works fine if I start the game with the enemy's already spawned whereas if the enemy's are spawned when my game is playing via the spawn script at the bottom of the page they dont destroy. I dont understand why this happens can anyone help me out?

Spawn script,

 using UnityEngine;

using System.Collections;

public class Spawn : MonoBehaviour

{

// Spawn location

public Vector3 spawnLocation = Vector3.zero;

// Spawn radius (Gives a bit more randomness factor to the spawn location)

public float spawnRadius = 1.0f;

// Spawn timer (seconds)

public float spawnTimer = 5.0f;

private float spawnTimeRemaining = 5.0f;

// The zombie to spawn

public GameObject zombiePrefab = null;

void Awake()

{

 spawnTimeRemaining = spawnTimer;

}

void FixedUpdate()

{

 spawnTimeRemaining -= Time.deltaTime;



 if (spawnTimeRemaining < 0.0f)

 {

   Vector2 circlePosition = Random.insideUnitCircle * spawnRadius;

   GameObject.Instantiate(zombiePrefab, spawnLocation + new Vector3(circlePosition.x, 0.0f, circlePosition.y), Quaternion.identity);



   spawnTimeRemaining = spawnTimer;

 }

}

}

These are the two scripts on my bullets,

 var bloodSplat : GameObject;

var explosion : GameObject;

function OnCollisionEnter (hit:Collision){

  if(hit.collider.tag == "Enemy"){



      var expl = Instantiate(bloodSplat, transform.position, Quaternion.identity);

      Destroy(gameObject);

      }

      

      else

      

      var bloo = Instantiate(explosion, transform.position, Quaternion.identity);

 Destroy(gameObject); 

      

}

 function OnCollisionEnter(myCol: Collision){

if(myCol.gameObject.name == "Enemy"){

Destroy(myCol.gameObject);

}

}